1. Field of Invention
The present invention relates to an image display apparatus that includes an image input device that receives a video signal, a video display that displays an image based on an input signal from the video input device, and a video signal adjusting device that adjusts a display setting of the video display based on a signal mode of the input signal.
2. Description of Related Art
Conventionally available image display apparatuses each include a video input device that receives a video signal and a video display that displays an optical image based on a video signal from the video input device. When a computer or a video cassette recorder is connected to such an image display apparatus, the video signal from the computer is displayed on a large screen such as a projection screen. This structure constitutes a computer-based multi-media presentation system.
Since a variety of computers may be connected to the image display apparatus, the image display apparatus is adjusted beforehand to match input signal modes that correspond to the computer that is likely to be connected.
Even if resolution and refresh rate are identical, a horizontal frequency of a video signal may be different from computer to computer. Even if the horizontal frequencies are identical, computers may be still different in the front porch and back porch of the horizontal blanking period and the synchronization margin of the horizontal synchronization signal. When a new computer is connected to the image display apparatus, the image display apparatus is switched on. During an operation, a user must fine-adjust settings in tracking, synchronization, display position and the like in a predetermined signal mode on the video display, each time any change takes place in the input signal, which would possibly be caused by switching the computer, from one type to another.
A system has been contemplated which performs fine adjustment of the display setting of the video display when a change takes place in the signal input to the image display apparatus. In such a system, however, the fine adjustment takes time, particularly, a tracking adjustment is time-consuming. Thus, this system is not a practical choice.
It is therefore an object of the present invention to provide an image display apparatus, which includes a video input device that receives a video signal, a video display that displays an optical image based on an input signal from the video input device, and a video signal adjusting device that adjusts the display setting of the video display based on a signal mode of the input signal, and which efficiently adjusts the video display even when a change takes place in the input signal.
To achieve the above object, the image display apparatus of the present invention only performs an automatic adjustment of the video display in a predetermined situation. Specifically, the image display apparatus of the present invention includes a video input device that receives a video signal, a video display that displays an optical image based on an input signal from the video input device, and a video signal adjusting device that adjusts the display setting of the video display based on a signal mode of the input signal. The image display apparatus also includes a determining device that causes the video display adjusting device to adjust the display setting of the video display when the input signal changes. The determining device includes an apparatus startup detector unit that detects whether a startup of the image display apparatus creates a change in the input signal. The determining device also includes a signal change detector unit that detects the change in the input signal. The determining device determines whether to cause the video display adjusting device to adjust the display setting, by referring to the combination of states detected by the apparatus startup detector unit and the signal change detector unit.
Since the image display apparatus of the present invention is provided with the determining device that determines whether to cause the video display adjusting device to adjust the display setting in response to a change in the input signal, the video display adjusting device performs an automatic adjustment only when it is needed. The display adjustment of the video display is thus efficiently performed. With its apparatus startup detector unit, the determining device determines whether any change takes place in the input signal in response to a startup of the image display apparatus. The determining device causes the video display adjusting device to automatically adjust the display setting in response to the change in the input signal at the startup.
The image display apparatus is also provided with a signal mode memory that stores the signal mode that the video display used at a power shutdown. When the apparatus startup detector unit determines that a change in the input signal has occurred at the startup, the determining device retrieves the signal mode stored in the signal mode memory to cause the video display adjusting device to adjust the display setting.
The signal mode memory is preferably a non-volatile memory that retains its data when power is removed, for example, EPROM (Erasable Programmable Read Only Memory) or EEPROM (Electrically Erasable Programmable Read Only Memory).
Since the video display adjusting device performs an automatic adjustment by retrieving the signal mode that was used at the last power shutdown, the display setting of the video display at the power shutdown is reused. The video display setting can thereby efficiently adjust the display setting.
When the signal change detector unit detects no signal change, the determining device causes the video display adjusting device to not adjust the display setting.
Since the determining device has an option to cause the video display adjusting device to not perform an automatic adjustment, the determining device performs the automatic adjustment only when it is needed.
The determining device includes a pre-change signal detector unit that detects the presence or absence of the input signal prior to the signal change when the signal change detector unit detects the signal change. The determining device preferably determines whether to cause the video display adjusting device to perform the adjustment, by referring to the state detected by the pre-change signal detector unit.
The absence of the input signal prior to the change may be detected when the computer that outputs the video signal is switched on subsequent to the startup of the image display apparatus, or when the computer is connected to the video input unit of the image display apparatus subsequent to the startup of the image display apparatus. The presence of the input signal prior to the change may be detected when a plurality of computers, that are connected to the image display apparatus, are selectively switched from one to another, or when the setting of the video signal is modified in the computer currently outputting the video signal.
Since the determining device is provided with the pre-change signal detector unit, the determination of whether to cause the video display adjusting device to adjust the display setting is as follows.
{circle around (1)} When the presence of a pre-change signal is detected, it is considered likely that the computer was selectively switched, or that the setting of the video signal was modified. The video display adjusting device performs the automatic adjustment, because the signal mode of the input signal changed, or because the change of the computer type changed the display setting data.
{circle around (2)} When the absence of a pre-change signal is detected, it is considered likely that the computer that outputs the video signal was switched off and then on again, after the startup of the image display apparatus, or that the computer was reconnected to the video input unit. The computer could possibly be the one with which the display setting was once established. The determining device examines the signal modes of the computers that had previously been connected thereto, and adopts the display setting data if it agrees with the signal mode of the currently connected computer, rather than causing the video display adjusting device to immediately perform the automatic adjustment.
Since the video display adjusting device performs the automatic adjustment in a limited way, the display setting of the video display is efficiently adjusted.
The image display apparatus further includes a display setting memory that stores the display setting data of the video display in accordance with the type of a signal mode of a likely video signal, and the type of tracking information, wherein the display setting data of the video display includes tracking information for the horizontal synchronization adjustment of the video display. The determining device includes a tracking information comparator unit that retrieves the tracking information of the input signal subsequent to the signal change, and compares the tracking information with the tracking information of the display setting stored in the display setting memory, when the pre-change signal detector unit detects no input signal prior to the signal change. The determining device determines whether to cause the image display adjusting device to adjust the display setting, by referring to the comparison result provided by the tracking information comparator unit.
With its tracking information comparator unit, the image display apparatus compares the tracking information before the change to the tracking information after the change, and only causes the video display adjusting device to adjust the display setting when there is no match between them. The video display adjusting device thereby performs the adjustment more efficiently.